Help with Zimbra install - DNS issues mainly

I have set up a Hyper-V VM with Ubuntu and installed Zimbra 8.0.0 into it but I am still having issues.

At the moment if I send a test email I get the below response:

Code:

This is the mail system at host vmmail.localhost.
I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can delete your own text from the attached returned message.
The mail system
<gsmith@gsmith.biz>: Host or domain name not found. Name service error for
name=vmmail.localhost type=A: Host not found

So I started looking at this guide and noticed the following:
If I run the following command